The present invention relates to a scooter type motorcycle.
In general, a power unit mounted on the scooter type motorcycle is structured such that a V-belt type transmission unit is uniformly connected to a rear portion of an engine unit, and a rear wheel is supported directly to an aftermost portion of the transmission unit
A front portion of the power unit (a portion of the engine unit) is pivoted to a body frame, and a rear portion (a portion of the transmission unit) is suspended to the body frame via a shock absorber, whereby a whole power unit vertically swings together with the rear wheel, and serves as a swing arm of the rear wheel.
In accordance with the structure mentioned above, there are advantages that a great capacity of an article accommodation box placed above the power unit may be obtained as well as an improved riding comfort may be obtained by making a vibration of the engine unit hard to transmit to the body frame.
On the contrary, however, a weight of the whole power unit will be increased when an engine displacement is increased, and a load to the rear wheel will also be increased; so that a load distribution between the front and rear wheels becomes improper.
Moreover, a rigidity for supporting the rear wheel becomes insufficient, whereby there is a problem that a steering performance and a riding stability are deteriorated.
Accordingly, as shown in Japanese Patent Application Laid-Open Publication Nos. 10-324287 and 11-129969, there has been developed a motorcycle with the engine unit and the transmission unit fixed to the body frame, and only a shaft drive unit extends rearward from the transmission unit which swings vertically, thereby driving the rear wheel.
With the structure mentioned above, it is possible to mount the engine unit, i.e. a heavy load, close to the front portion of the body frame in the same manner as that of the ordinal type motorcycle so as to make the load distribution between the front and rear wheels proper.
In this embodiment, a center axis of the cylinder bore of the engine unit is tilted forward substantially along the longitudinal direction of the vehicle body, whereby a height of the engine unit is reduced.
In order to mount the engine unit close to the front portion of the body frame in the scooter type motorcycle, a center console must be formed, and the engine unit must be arranged so as to extend from the inner portion of the center console toward the lower portion of the seat.
However, since the center console is generally formed in the center of the low bottom floor type step board provided between the handle bar and the seat, heights of the center console may restrict a size of a footing space over the step board and an ability to get on and off easy onto the motorcycle is deteriorated.
In particular, in the embodiment of mounting a four-cycle type engine unit having a large engine displacement provided with a balancer shaft for reducing a vibration, a lot of auxiliary devices such as the balancer shaft, a generator, a starter motor and the like are placed, whereby a whole engine unit tends to be large-scaled, and further, since it is necessary to provide the auxiliary devices above the engine unit with taking a water tightness into consideration, the size of the footing space is further restricted.
Furthermore, in this kind of motorcycle (the scooter type), the seat hinge is generally provided at the front end of the seat and the article accommodation box below the seat is accessible by rotating the seat upwardly around the seat hinge.
However, in order to obtain the large footing space over the step board, the height of the frame pipe composing the body frame becomes inherently lower than the position of the seat, so that it is necessary to stand up an extension upward extending high from the frame pipe for the purpose of supporting the seat hinge of the seat, which makes it impossible to support the seat hinge with a high rigidity.
An object of the present invention is to substantially eliminate defects or drawbacks encountered in the prior art described above and to make it possible to place a seat hinge at a front end of a seat in a body frame with a high rigidity, and to make it easy to replace an oil filter.
This and other objects can be achieved according to the present invention by providing a motorcycle comprising a low bottom floor type step board provided between a handle bar and a seat, an engine unit arranged so as to extend from an inner portion of a center console provided in a center portion in a vehicle width direction of the step board toward a lower portion of the seat, the engine unit structured such that a cylinder head, a cylinder block and a crankcase are combined in order from a front, a center axis of a cylinder bore formed in an inner portion of the cylinder block substantially extends along a vehicle body longitudinal direction, and a crankshaft and a balancer shaft are provided along the vehicle width direction substantially perpendicular to the center axis of the cylinder bore, the motorcycle comprising:
the crankshaft and the balancer shaft supported on a matching surface between the cylinder block and the crankcase,
the balancer shaft arranged above the crankshaft,
auxiliary devices of the engine unit placed in front of and behind the balancer shaft, wherein
the auxiliary devices with smaller outer diameters among the auxiliary devices is arranged in front of the balancer shaft,
the auxiliary devices with larger outer diameters is arranged behind the balancer shaft, and
an oil filter is provided in a lower portion of the cylinder block.
In preferred embodiments, the motorcycle further comprising a pair of right and left frame pipes passing through an inner portion of the center console curved along upper profiles of the cylinder head, the cylinder block and the auxiliary devices.
Further, the motorcycle comprising a pair of right and left frame pipes passing through the inner portion of the center console connected between portions passing through above the auxiliary devices having larger outer diameters placed in the upper portion of the engine unit by a cross member extending in the vehicle width direction, the cross member positioned below a portion near a front end of the seat, the frame pipe disposed in front of the cross member inclined forward downward, and a seat hinge at the front end of the seat provided at an upper end of an extension protruded above from the cross member.
Furthermore, the auxiliary device arranged in front of the balancer shaft is a starter motor, and the auxiliary device arranged behind the balancer shaft is a generator.
According to the motorcycle of the present invention of the characters described above, since the auxiliary devices are provided in the upper portion of the engine unit, it is possible to secure an improved water tightness of the auxiliary devices.
Further, the oil filter is provided below the engine unit, whereby oil dropping down at a time of replacing the oil filter will not drop onto the engine unit, so that it is easy to replace the oil filter.
Furthermore, even in the case that the oil filter is positioned below the engine unit, whereby a space above the engine unit is reduced, the auxiliary devices having the small outer diameters are arranged in front of the balancer shaft, whereby it is possible to keep the height of the center console to a low level and it is possible to obtain a large footing space.
Moreover, since the height of the frame pipe passing through the inner portion of the center console is reduced, it is possible to sufficiently reduce the height of the center console so as to obtain a large footing space, and it is possible to reduce a distance between the cross member connecting between the right and left frame pipes and the seat hinge at the front end of the seat so as to reduce the length of the extension, thereby placing the seat hinge in the body frame with a high rigidity.
Further, the starter motor has an outer diameter smaller than that of the generator, generally, it is possible to reduce the height of the center console on the basis of the structure mentioned above so as to obtain a wide footing space.